1. Field of the Invention
The present invention relates to an end face polishing apparatus that polishes an end face of a rod-shaped member such as fibers for optical communication and a ferrule holding fibers for optical communication.
2. Description of the Background Art
Fibers for optical communication are adhesively secured in the central hole of a ferrule, a main member of a connector, and then the ferrule end face and the end face of fibers are polished together and thus finished into a smooth, mirror surface. If the polished end faces of the ferrule and the fibers are not vertical to the central axis of the ferrule or if there is a flaw on the polished faces, the precision in positioning such ferrules as they are connected facing each other in an optical connector is lowered, and the loss increases. Therefore, the face of the ferrule including the optical fibers must be polished with high precision.
A conventional apparatus for polishing the end faces of optical fibers is disclosed for example by Japanese Patent Laid-Open No. 26456/1991. The disclosed end face polishing apparatus includes an eccentric adapter that rotates on a circle concentric with a rotating disc, and a planetary gear that transmits the rotation of a revolution motor to the eccentric adapter. These elements are coupled in a lapping board, so that the lapping board is allowed to rotate and revolve, while the end faces of a plurality of ferrules held by a polishing fixture are pressed against a lapping member secured to the lapping board by a supporting portion provided at the main body of the apparatus.
In the conventional end face polishing apparatus, however, the position for pressing the polishing fixture by the supporting portion and the position for polishing the rod-shaped member are different in height, so that a moment is applied upon the polishing fixture as the polishing fixture is pressed, and the operation becomes unstable. The end face of the bar-shape member is therefore polished into a curved surface, and when a ferrule is used as the rod-shaped member, the polishing precision of the ferrule could be low. As a result, when end faces are connected in abutment with each other in optical connection, optical insertion loss could be large.
In a multi-fiber optical connector as a ferrule holding a plurality of optical fibers, the curved surface resulting from using the conventional end face polishing apparatus could increase insertion loss caused by optical connection of optical fibers particularly on the outer periphery when end faces of the multi-fiber optical connectors are abutted against each other.
Furthermore, in the conventional end face polishing apparatus, the polishing fixture should be secured free from inclination in order to polish the end face not to be curved, while the precision of securing the polishing fixture and the precision of attaching the rod-shaped member to the polishing fixture must be high, which requires much time and complicated operation.
The present invention overcomes the foregoing disadvantages in the conventional art, and it is an object of the present invention to provide an end face polishing apparatus that allows a rod-shaped member to be polished with improved precision and the polishing process to be simplified.
According to a first aspect of the present invention directed to a solution to the above disadvantages, in an end face polishing apparatus polishing an end face of a rod-shaped member mounted at a polishing fixture by pressing the rod-shaped member against a lapping member on a lapping board supported at the main body of the apparatus to rotate and rock, the polishing fixture is pressed through an abutting part against a supporting portion provided at the apparatus main body, and the abutting part is located more on the side of the lapping board than the center of gravity of the polishing fixture.
According to a second aspect of the invention, in the end face polishing apparatus according to the first aspect, the abutting part is within the range of xc2x15.0 mm from the polishing surface of the lapping member in the pressing direction.
According to a third aspect of the invention, in the end face polishing apparatus according to the first or second aspect, the abutting part is located about in the center of the polishing fixture. Here, the abutting part may be provided in at least two, preferably at least four positions at the outer periphery of the jig, and still the same effect can be provided
According to a fourth aspect of the invention, in the end face polishing apparatus according to any one of the first to third aspects, a recessed portion is provided near the center of the lapping board on the side of the polishing fixture, and the abutting part of the polishing fixture against the supporting portion is provided to project into the recessed portion.
According to a fifth aspect of the invention, in the end face polishing apparatus according to any one of the first to fourth aspects, the rod-shaped member is a ferrule including a ferrule tubular body for holding optical fibers and a collar member provided at a rear end of the ferrule tubular body for holding coated optical fibers.
According to a sixth aspect of the invention, in the end face polishing apparatus according to the fifth aspect, the ferrule is a multi-fiber optical connector.
According to a seventh aspect of the invention, an end face polishing method includes pressing an end face of a rod-shaped member against a surface of a rotating and revolving lapping member, and securing the rod-shaped member by an abutting part extended in the radial direction of the rod-shaped member and about in the same level as the surface of the lapping member.
According to an eighth aspect of the invention, a polishing fixture has a through hole for receiving a rod-shaped member in the center, an abutting part at the outer periphery for pressing from the upper surface to the bottom surface, and a recessed portion at the bottom surface in the center.
According to a ninth aspect of the invention, a method of polishing an end face of a rod-shaped member includes the steps of securing a polishing fixture having a through hole for receiving a rod-shaped member in the center, an abutting part at the outer periphery for pressing from the upper surface to the bottom surface, and a recessed portion at the bottom surface in the center, providing the upper surface of a lapping member facing the bottom surface in the center about in the same level as the upper surface of the polishing fixture, and rotating and revolving the lapping member.
According to the present invention, the abutting part where the polishing fixture is pressed by the supporting portion is located below the center of gravity of the polishing fixture, and therefore the moment applied on the polishing fixture can be reduced. In this way, the periphery of the polishing fixture can be prevented from being deviated from the lapping board in the vertical direction, and the polishing surface of the rod-shaped member can be polished perpendicularly to the axial direction.